adjective: (participial adjective; editing, typography) (not comparable) Having been run in before or behind previous text.
adjective: (participial adjective; mechanical, engineering) (sometimes comparable) Having been run in to seat the parts.
verb: (transitive, informal, chiefly passive) To arrest; (especially) to track down and arrest.
verb: (transitive, Britain) To use new machinery at less than full speed, preventing damage.
verb: (figuratively) To start a new regime slowly.
verb: (rugby) To score (a try).
verb: (typography, printing) To insert (a word, etc.) without making a line break or new paragraph (so that it is not free-hanging).
verb: (printing) To alter the position of matter to fill vacant space.
noun: Alternative spelling of run-in (omitting the hyphens from nouns of this type is nonstandard in formal publications but widely seen in unedited writing) [An encounter; a scrape or brush, especially one involving trouble or difficulty.]